Research Of White LED Visible Light Communication Receiver System

The visible light communication using white LED (VLC-LED) is an emerging technology, which can replace RF communications in the case of electromagnetic interference restricted. Because the receiver can detect, recover and process signals, the communication performance of VLC-LED system is determined by receiver's SNR. However, the beam angle of LED is so large that is not easy to collect, and light has been very weak when reaches the receiver after propagating through space, so optical antennas need to be set before the photodetector to cellect lights and enhance the signal strength. The compound parabolic concentrator (CPC) can collect the light within the acceptance angle as the concentration ratio close to the desired receiver, and CPC has characteristics of wide field and high concentration, so CPC meets the need of VLC-LED. Primary condensers such as hemispherical lens is used to collect light in the VLC-LED system by many researchers at present, but the effect is not very obvious. That setting CPC as visible light communication optical antennas is the main contents of this thesis:First, the structure and concentrating principle of standard CPC is analyzed in this article. The Monte-Carlo ray tracing method is used to research the relationship between four factors and CPC optical receiving performance, and the four factors include maximum acceptance angle, communication distance D, observation distance H and offset angle. The result shows that, when maximum acceptance angle is little, the concentration ratio is high and the volume of CPC is great, and offset angle is little at the same time.The mathematical model of non-standard CPC is established, and the effect of amputated rate, maximum acceptance angle and material on CPC concentrating characteristics is analysed. As a result, the reasonable interception range is 1/3 to 1/2.The optical receiver antenna of VLC-LED system based on non-standardized compound parabolic concentrator is designed, whose exit radius is 11mm, the acceptance angle is 25°and the amputated rate is 1/2. The simulation results show that the volume of optimized CPC is decreased by nearly 45% than corresponding standard CPC, while the total receiving lumens is decreased by just 16%-18%, so the condensing efficiency has been improved.At last, the simulation comparative experiments of optimized CPC, hemispherical condenser and fresnel lens is carried out in the same conditions. The results show that optimal CPC receiving light intensity value is 60.1% higher than the hemispherical lens and of 31.78% higher than fresnel lens. So the concentration ratio of CPC is high, but its condenser uniformity is general because of a ring in the focal plane.The non-standard CPC designed in this paper has the advantages of small size, high condenser, simple structure,low cost and easy to install and so on. The research work provides a good theoretical basis for design and production of optical receiver with excellent performance of white VLC-LED.